Watch case base and method for making same

ABSTRACT

Back of a watch case including a cover ( 4 ) that defines the external surface of the back, and a false back ( 11 ) that is mounted against the internal surface of the cover. The false back can be provided with an engraved decoration and can be manufactured by stamping from a plate of even thickness. A transponder can be housed between the cover and the false back.

This invention relates to the back of a watch case and a process ofmanufacture of the back of a watch case. This invention in particularrelates to the back of a watch case with an internal surface that isprovided with decoration.

Watch cases comprise a middle and a back that can be screwed or clippedonto the middle. The back must be able to be opened to access the watchmovement, for example to replace a battery or for repairs or maintenanceof the movement. Many luxury watch cases are provided with a back, ofwhich the aesthetic aspect of the internal surface is carefully done.For example, backs of watch cases are known with an internal surfacethat is provided with decoration, for example an engraved pattern, or byornamentation with guilloche into the thickness of the metal.

The backs of watch cases are most often produced by punching. Theinternal surface of the backs of watch cases is generally concave andhas indentations or threads for attachment to the middle and to maintaina seal. It is therefore difficult to automate decoration of thissurface. For this reason, the decoration of the internal surface of theback is most often done manually. Guilloche back patterns that arehighly valued are generally done using a special graver and a smallhammer in order to make more or less regular circles in the thickness ofthe back. These operations are very expensive.

One object of this invention is to propose a back of a watch case and aprocess of manufacture of the back of a watch case that has the sameaesthetic qualities as the known decorated backs of watch cases but thatcan be produced at a lower cost.

Moreover, watches containing an identification element, for example atransponder, which can be interrogated via an inductive reading device,are already known. Transponders are used especially to store informationthere that gives access to protected areas, for example as anidentification element in a business or as a movie admission ticket orfor ski lifts. It has likewise already been suggested that the serialnumber of the watch be inscribed in the identification element in thewatch. These data can be read for example by the after-sales servicedepartment to check the series to which the watch belongs. Thus, theidentification element makes it possible to replace or complete theserial number ordinarily engraved on the back of watch cases.

In a watch, the antenna of the transponder is generally installed justover or under the face or sometimes in the bezel; these arrangementssometimes engender major restrictions, given the small space availablein a watch, and do not allow marking of watches comprising a metalliccase. Moreover, the antenna is generally visible: this is notattractive, and it is exposed to impacts and vibrations. For thesereasons, placing the transponder against the internal surface of theback of the watch would be preferable. This arrangement is sometimeincompatible with the decorated backs of watch cases. Moreover, thetransponder and especially its antenna are subject to the risk of damagewhen the back of the case is opened carelessly.

Another object of this invention is thus to propose a back of a watchcase that makes it possible to incorporate a transponder or some otheridentification element.

These objects are achieved by way of a back of a watch case and aprocess of manufacture with the claimed characteristics.

In particular, these objects are achieved by way of a back of a watchcase comprising a cover that defines the external surface of the back,and a false back mounted against the internal surface of said cover.

This approach has the advantage of separating the manufacture of thecover, which often requires punching operations, tapping operations,etc., from production of the false back that requires other, simplerstamping operations (cutting) and decoration operations. It is thuspossible to optimize the processes used for production of these twoelements.

In particular, it is possible to produce the false back by cutting on aplate of even thickness that has been decorated beforehand. Thedecoration of a plate of even thickness can be automated and performedusing a machine.

It is thus possible to decorate, in a single operation, a plate that isintended for production of several tens of false watch backs. Decorationcan be done, for example, by engraving in the thickness of the plate.

This approach, moreover, has the advantage of allowing an electronicidentification element to be placed between the cover and the falseback. This identification element can be completely hidden between thecover and the false back. It has no adverse effect on the internal orexternal aesthetics of the watch and is completely protected against anydamage, even in the case of opening the back. Moreover, the false backcontributes to increasing the strength and rigidity of the back; it isthus possible to reduce the thickness of the cover, which offers theadvantage of facilitating inductive reading through the back. Thisadvantage is especially important in the case of a back of a watch casemade of metal that highly attenuates radio waves transmitted to and fromthe transponder.

The prior art discloses watches with a back that includes additionalelements. In particular, CH 335610 describes a watch that has a back,i.e., an element that closes the middle in a stationary manner, on theexternal surface of which a lining of synthetic material is added,intended mainly to protect the watch from marks in case of contact withforeign bodies. However, this lining is not comparable to the falsebacks of this invention. In particular, this lining is located on theexternal surface of the back of the watch and not on its internalsurface. Thus, it cannot in any way contribute to reducing the costsincurred by decoration of the internal surface of the back of the watch.

U.S. Pat. No. 1,404,656 describes a watch with a case that is composedof a precious metal outer case, reinforced, among others, by an internalcase of a less expensive material. The case of this watch, however, doesnot comprise a back allowing easy access to the movement withoutremoving the latter from the case. Moreover, the internal case iscompletely hidden by the external case and does not perform anyaesthetic function.

The invention will be better understood by reading the description thatis given by way of example and illustrated by the attached figures,among which:

FIG. 1 is a cutaway view of a rough plate intended for production ofseveral false backs according to the invention.

FIG. 2 is a cutaway view of the same plate during the operation ofdecoration by engraving of the upper surface.

FIG. 3 is a top view of the plate after decoration, showing a guillochepattern.

FIG. 4 is a cutaway view of the plate during the operation of cutting bystamping.

FIG. 5 is a top view of a false back of the watch that is decorated andcut according to the invention.

FIG. 6 is a partial cutaway view of a watch case provided with a firstvariant of a watch back according to the invention.

FIG. 7 is a partial cutaway view of a watch case provided with a secondvariant of a watch back according to the invention.

FIG. 1 shows a plate 1 of even thickness that is intended for productionof a plurality of decorated false backs of watch cases in a reducednumber of operations. The plate is preferably metal, preferably the samemetal as the one used for the back of the watch.

The upper visible surface of the plate is decorated in a singleoperation, for example by way of a stamp 2 pressed against the entiresurface of the plate 1 and provided with a punch 20 (FIG. 2). The sizeof the stamp 2 can correspond to that of the plate 1, as shown in FIG.2, or can be smaller and applied several times. It is also possible toengrave the upper surface of the plate 1 by passing it between tworollers, one with a relief pattern, or to apply decoration to the plate1 by another process, for example by screen printing, plating,anodizing, etc. Preferably, however, surface treatment of the plate thatis identical to that used for the other parts of the back is to bechosen, in order to make the use of a false back as inconspicuous aspossible.

FIG. 3 shows the upper surface of the decorated plate 1. In thisexample, the pattern 10 applied by stamping resembles known guillochepatterns.

The plate 1 is then cut, preferably by way of a punch 3 as shown in FIG.4. It is, of course, also possible to cut several false backs at thesame time on the same plate and/or to cut and decorate the plate 1 in asingle operation and using the same stamp. It is also possible toperform several separate decorating operations on the same plate 1.

Moreover, additional machining operations that are not shown can beperformed on the false back 11, for example to mill a cavity (shown inFIGS. 6 and 7) that is intended to house an electronic component, forexample an identification element 5 and a coil 6. This cavity can alsobe obtained by stamping. It is also possible to deform the lower surfaceof the false back by stamping in order to adapt it to the internal shapeof the cover.

FIG. 5 shows a top view of a false back 11 of a watch decorated by wayof a guilloche pattern 10.

FIG. 6 shows a partial sectional drawing of a watch case comprising amiddle 7 and a back 11, 4 according to a first variant of the invention.The back includes a cover 4 and a false back 11 that has been producedusing the above-described process. The cover and the false back areprovided with holes for screws 40 for attachment to the middle 7. A seal70 makes it possible to prevent infiltration of water between the middleand the back. In this example, an identification element composed hereof a transponder 5 equipped with an antenna 6 is housed in a cavitybetween the false back 11 and the cover 4. The thickness of the cover 4is preferably reduced in order to limit the attenuation of theelectromagnetic field through this wall. Definitive tests were performedwith a cover thickness of roughly 5 to 7 tenths of a millimeterdepending on the material used. The rigidity and strength of the backare nevertheless guaranteed thanks to the false back 11 that can becemented onto the cover 4 or simply attached using screws 40.

The antenna 6 is composed of a coil formed by winding a copper wire andconnected by bonding directly to the lugs of the circuit 5. The circuit5 can be fixed in the cavity by way of a two-sided self-adhesive filmstamped to the size of the adhesive housing. The circuit 5 placed on theself-adhesive film is transported by suction to be deposited on thebottom of the recess. Especially during this operation, special caremust be taken to avoid breaking the antenna wire, and, if necessary, itwill be possible to check proper operation of the identificationelements by reading its contents after installation.

The circuit 5 can, moreover, be coated with resin. Definitive tests wereperformed by supplying an exact amount of very pure epoxy resin via ametering apparatus. To ensure that the resin spreads perfectly as itfills the cavity, a centrifuge or a vibration device could be usedduring polymerization of the resin.

It is especially important to prevent the rising of the resin duringpolymerization from breaking the wires of the antenna 6. To avoid thisrisk, for example, polymerization should proceed slowly as the back 11,4 is stored at ambient temperature for at least 24 hours or as it isheated to a moderate temperature, roughly 35° C.

The identification element 5 is preferably supplied with electricitysolely by the inductive writing device and/or reading-writing deviceused to access the stored data, without calling on the watch battery. Itcomprises a modulator-demodulator, which is not shown, to receive anddemodulate the signals of the inductive reading-writing device, and tomodulate and transmit the responses. In the case of a metallic back, thecircuit 5 preferably uses a frequency that is distinctly lower thanthose ordinarily used for standard RFID elements, preferably a frequencyof less than 50 kHz, in order to allow transmission through the metal.An encryption and/or electronic signature module can, moreover, beprovided in the circuit 5 in the case in which confidential data, forexample medical data or amounts of money, should be stored in one ormore fields of the memory zones.

The circuit 5 preferably comprises a memory zone that is not shown,including a program area as well as a data area. The watch back can thusbe personalized by writing the data of the manufacturer and/or theretailer (serial number, date of manufacture, lot number, etc.) in thedata area. Personalization can be done by the manufacturer of the watchafter the back is mounted on the watch or more easily by themanufacturer of the backs before assembly of the watch on the databaseand serial numbers provided by the watch manufacturer, for example, on adiskette or via e-mail. The memory zone can also be modified by theapplication suppliers after sale of the watch, for example to writeaccess codes there for the protected areas.

In one preferred variant of the invention, the serial number of thewatch is, moreover, engraved on the external surface of the back. Thischaracteristic makes it possible to check the serial number of the watchwithout the special reading device.

FIG. 7 shows a second variant of the back of the watch case providedwith a false back 11 according to the invention. In this variant, thecover is provided with peripheral threads 41 that allow it to be screweddirectly onto the middle 7. A seal 42 between the middle 7 and aprojection 42 of the cover make it possible to prevent infiltration ofwater. As in the variant above, the false back 11 is placed on the cover4 and secured, for example, by cementing. An identification element 5, 6can be placed between the cover 4 and the false back 11.

One skilled in the art will understand that other systems of attachmentof the back to the middle, by clips or via screws, can be used withinthe framework of this invention.

1. Back of a watch case comprising a cover (4) that defines the externalsurface of the back, characterized by a false back (11) installedagainst the internal surface of said cover.
 2. Back of a watch caseaccording to the claim 1, wherein said false back (11) comprises adecoration (10) on the mirror-side surface.
 3. Back of a watch caseaccording to claim 2, wherein said decoration (10) is marked in thethickness of said false back (11).
 4. Back of a watch case according toclaim 1, wherein said false back (11) has an even thickness and whereinsaid cover (4) comprises means of attachment (40, 42) to the middle (7)of the watch case.
 5. Back of a watch case according to claim 1, whereinsaid false back (11) is attached securely against said internal surfaceof said cover (4).
 6. Back of a watch case according to claim 1, whereinan identification element (5, 6) is installed between said cover (4) andsaid false back (11).
 7. Back of a watch case according to claim 1,wherein said identification element comprises an electronic circuit (5)and an antenna (6) installed in a cavity between said cover and saidfalse back.
 8. Back of a watch case according to claim 7, wherein saidelectronic circuit (5) is fixed in said cavity by way of a double-sidedadhesive.
 9. Back of a watch case according to claim 7, wherein saidelectronic circuit (5) is coated with resin.
 10. Back of a watch caseaccording to claims claim 1, wherein said cover (4) and/or said falseback (11) are metal.
 11. False back (1) intended to be installed againstthe internal surface of a cover (4) of the back of a watch case andcomprising a surface provided with decoration (10).
 12. Process ofproduction of the back of a watch case, comprising the following step:installation of a false back (11) against the internal surface of thecover (4) of the back.
 13. Process according to claim 1, comprising,moreover, a prior step of stamping of said false back (11) from a plate(1) of even thickness.
 14. Process according to claim 13, comprising,moreover, a prior step of engraving of a decoration (10) on one surfaceof said plate.
 15. Process according to claim 12, comprising, moreover,a step of insertion of an electronic identification element (5) betweensaid cover (4) and said false back (11).